Composite materials comprised of particles of a hard constituent phase and a binder phase binding the particles together are common and are referred to as "composite materials" or "composite substrates" hereinafter. Such materials also may be referred to as "cemented" composite materials and include, for example, ceramics, cermets, and cemented carbides. Cemented carbides, include, for example, materials composed of a hard particulate material such as, for example, particles of one or more of tungsten carbide (WC), titanium carbide (TiC), titanium carbonitride (TiCN), tantalum carbide (TaC), tantalum nitride (TaN), niobium carbide (NbC), niobium nitride (NbN), zirconium carbide (ZrC), zirconium nitride (ZrN), hafnium carbide (HfC), and hafnium nitride (HfN) cemented together by a binder phase that is composed predominantly of one or more of cobalt, nickel, and iron.
Metal cutting inserts fabricated from composite materials are commonly used in chip cutting machining of metals in the metal machining industry. Metal cutting inserts are commonly fabricated from particles of metal carbide, usually tungsten carbide with the addition of carbides of other metals such as, for example, niobium, titanium, tantalum, and a metallic binder phase of cobalt or nickel. The carbide materials provide high strength but still may wear quickly when used in, for example, milling and other metal machining operations. By depositing a thin layer of wear-resistant material on the working surfaces of cemented carbide cutting inserts it is possible to increase the wear-resistance of the inserts without adversely affecting toughness. Commonly used wear-resistant cemented carbide insert coatings include, for example, TiC, TiN, TiCN, and Al.sub.2 O.sub.3. Such wear-resistant coatings reduce the erosion and corrosion of the inserts' binder material.
The utility of coated composite materials such as coated cemented carbides is limited by the strength of adhesion of the wear-resistant coating to the composite material. Absence of strong adhesion between wear-resistant coatings and metal cutting inserts causes delamination of the coatings from the inserts, decreasing the inserts' service life. The presence of cobalt at the inserts' surfaces also increases the tendency of the coatings and substrates to experience delamination during use. Accordingly, it would be advantageous to provide a novel method for increasing the adhesion of wear-resistant coatings to composite materials. More broadly, it would be advantageous to enhance the adhesion of wear-resistant coatings and other types of coatings to composite material and other types of substrates.